A group of teenagers in Canada allegedly deceived girls into sending them lewd pictures through the photo-sharing application SnapChat and distributed them at school, police said.

Ten boys, ages 13 to 15, were detained by police in Laval, Quebec, on Thursday, CTV Montreal reports. Police say they coerced or tricked seven girls into posing for photographs that were then distributed at the school. Users of SnapChat can send photos that automatically disappear after a few seconds, but the boys captured the images with screenshots.

It’s unclear to what extent the images were distributed beyond the school. CTV reports that dozens of officers, including a special unit of 20 investigators, had been on the case leading up to Thursday’s bust.